The present invention relates to an apparatus and a method for handling substrates in a fluid tank in which the substrates can be placed at a distance from one another as sets, whereby a support strip can be placed on the upper edge region of the substrates. With apparatus as they are known, for example, from EP-B-0 385 536, U.S. Pat. No. 5,265,184, or DE-A-44 13 077 that originates with the applicant of this application, the substrates are held by a substrate-receiving apparatus in the fluid tank or in a substrate holder either by means of a 3-point support or with a 1-point support and additional guide slots on the inner sides of the tank wall or slots in the walls of a hood. In the case of the 3-point support, the support of the substrates is limited to a narrow edge region on the underside of the substrates. Especially with the processing of large wafer dimensions or diameters, for example of 300 mm, such a support is, however, not reliable, since it is not possible to rule out that at least in the upper region, which is remote from the support, the wafers rest against one another, so that the rate of rejection is great. The contacting of adjacent substrates is particularly enhanced during removal of the wafers from the fluid due to the capillary action between the wafers. The use of guide slots and side holders in the fluid tank, or in a hood that is disposed above the fluid tank, has the drawback that the manufacturing costs for the tank and/or the hood are considerably greater. Furthermore, such slots adversely affect a flow of the treatment fluid in the tank that is as uniform and free of disruption as possible. Guide slots furthermore make it more difficult to clean and dry the tank and hood. However, even with the use of guide slots in the drying hood, especially for substrates having large dimensions, the introduction of the substrates into the slots is not ensured, especially due to the capillary action between the substrates that are raised out of the treatment fluid, so that as a consequence damage to the substrates can occur.
A further drawback of the known arrangements is that when the fluid flows rapidly into the tank below the substrates, there exists the danger that the substrates will be raised or will float. Thus, the reliable, parallel and spaced support of the substrates in the substrate-receiving apparatus, or in a substrate carrier, is not guaranteed.
U.S. Pat. No. 5,488,964 A1 discloses an apparatus of the aforementioned type where during the treatment in the fluid tank a rod or a plate is placed upon flat regions of the substrates in order to prevent the substrates from floating up. This rod or plate is first pivoted over the substrates via a drive mechanism when they are introduced into the fluid tank. Prior to removal of the substrates from the fluid tank, the rod or plate is again pivoted away in order to be able to remove the substrates from the fluid tank. Such an arrangement is very expensive and complicated, and more space is required over the fluid tank, especially with respect to the pivoting action. Furthermore, during the loading and unloading process, the substrates are not held by this rod or plate, so that the danger exists that the substrates can rest against and contact one another. It is an object of the present invention to provide an apparatus and method of the aforementioned type with which even substrates having large dimensions can be reliably supported during the processing and/or during the introduction and removal into or from the fluid tank.